Measurement and Motion Class 6
- 2. Physical Quantities • The quantities that can be measured are called physical quantities. For measuring the physical quantities, we require magnitude and a fixed unit. For example, If the distance from London to Reading is 275 km, so the magnitude is 275 and its unit is km here. • The specific physical quantities that cannot be expressed in any other quantity are called fundamental physical quantities. Some fundamental physical quantities are mass, length, time and temperature.
- 3. Traditional Units of Measurement In ancient times, people use their hands, arms and feet to measure the quantities. These methods still use in the present time. The units that we measure through these methods are yards, cubit and handspan. Units Description Yard The distance between the endpoint of an outstretched arm to the tip of the nose. Cubit The distance between the elbow to the tip of the middle finger. Foot Measurement of the quantity by a barefoot of an adult person. Handspan The measurement of a quantity by the tip of the thumb to the tip of the little finger when the palm is outstretched.
- 4. Standard Units of Measurement Quantities SI units Symbol Length metre m Mass kilogram kg Time second s The standard units of measurement introduced to measure accurate quantity of any object. In 1960, the General Council of Weights and Measures organized where all the scientists gathered to decide the uniform system of units acceptable all over the world.
- 5. Other SI systems • The measurement of smaller quantities is called submultiples of units. They represent with the factor of 1/10, 1/100 and 1/1000, etc. • The measurement of larger quantities is called multiples of units. They represent with the factor 10, 100 and 1000, etc. • Both multiples and submultiples have prefixes and symbol. Prefixes Symbol Submultiples/Multiples deci d Submultiple: 1/10 centi c Submultiple: 1/100 milli m Submultiple: 1/1000 Kilo k Multiple: 1000 Hecto h Multiple: 100 Mega M Multiple: 10000 Terms Description CGS Centimetre for length, Gram for mass and Second for time MKS Metre for length, Kilogram for mass and Second for time FPS Foot for length, Pound for mass and Second for time
- 6. Measuring Length The measurement of length concerns the length, width, thickness, height and distance of any object. There are several instruments used to measure the length. For example, a ruler, metre rod and a measuring tape, etc. • A ruler has units of centimeter and millimeter. It is used to measure smaller quantities • A meter rod is used by tailors to measure the length of the cloth. The unit of meter rod is fixed to one meter.
- 7. Measuring Length of a Curved Line The divider method 1 i. Take a pair of dividers and separate them with the help of a scale. 2 ii. Put the one tip of the divider at the one end of the curved line and another tip of divider at the curved line by taking markings. 3 iii. Repeat this process until the whole line is divided into segments. 4 iv. If any segment is left over then measure the length by a formula shown below. The thread method 1 i. Take a long thread and mark one of its ends. 2 ii. Put the marked end of the thread at the starting of the curved line by using your thumb. 3 iii. Put the other end of the thread to the other side of the curved line by another thumb of your other hand. 4 iv. Lastly, stretch the thread to measure the length. The length of a curved line : (Number of segments of equal lengths x distance between the tips of the divider) + length of the left-over part
- 9. Estimation The ability of guessing the value of anything without calculating the accurate value of the object is called the estimation. Eg: by planning a trip, we assume the approximate cost and time. Estimation helps in daily tasks when we must estimate time, money or any other quantity. When you're shopping in the grocery store and trying to stay within a budget, for example, you estimate the cost of the items you put in your cart to keep a running total in your head. Importance of Estimation in Real Life
- 11. Motion The changing in the position of any object concerning time regarding the effects of its surroundings is called a motion. For example, driving a car. If an object is fixed at a particular position, then there is no changing of the position called stationary or at the rest. For example, trees are fixed at a particular place. Living things move on their own, but non-living things do not move on their own. For example, a car needs a driver and fuel to move.
- 12. Rest and Motion are Relative. The state of being at rest or in motion is always relative to a certain object. For example: Suppose you and your father sitting in a car and your mother is standing in the street. When the car moves, your father is at rest to you but not to your mother.